Disable some new 'controversial' PMD rules, and enable some of the
others we had suppressed.

Change-Id: Ia15d78858617e8b4dcc71c47b91d9975118206a9
Reviewed-on: http://gerrit.dmdirc.com/3642
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

This was previously all under checkstyle/ which is weird as there's
a whole bunch of non-checkstyle stuff. Move everything into the nice
etc/ folder to keep it out of the way and sanely organised.

Change-Id: I0df52e8eddc6588c775a5173b624144807f1e59a
Reviewed-on: http://gerrit.dmdirc.com/3102
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>

Change-Id: I91a99b0e6cc6ae6feb7d80f853d60aa0f5c26d9a
Reviewed-on: http://gerrit.dmdirc.com/1575
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Greg Holmes <greg@dmdirc.com>